The present invention relates to an internal combustion engine suitable for use in small-sized vehicles such as motor cycles and, more particularly, to an intake system of four stroke cycle engine of a type having a combustion chamber, an intake passage and an exhaust passage opening to the combustion chamber and an intake valve and an exhaust valve disposed in the intake and exhaust passages, respectively, for opening and closing these passages.
Generally speaking, four stroke cycle engines operate more quietly and stably than two stroke cycle engines but can produce small output as compared with two stroke cycle engines having equal displacement.
Under this circumstance, the present invention aims at providing an intake system for four stroke cycle engines, capable of increasing the intake efficiency with a simple construction, thereby to overcome the above-stated problem of the prior art.
To this end, according to the invention, there is provided an intake system for internal combustion engine comprising a control passage means opening to a portion of the intake passage in the vicinity of the intake valve, and a supply chamber of a required volume and connected to the control passage means.
The above and other objects, features and advantages of the invention will become apparent from the following detailed description of the invention when taken in conjunction with the accompanying drawings which illustrates a few presently preferred embodiment of the invention.